Starting in April's Thunderbolts #172, the series begins a Thunderbolts vs. Thunderbolts arc which also happens to be occurring in conjunction with the 15th anniversary of the series. Writer Jeff Parker will be joined by artist Declan Shalvey with covers by Mark Bagley.
And here's what we learned about the arc:

The Thunderbolts' longtime writer Jeff Parker says that the story grew organically out of the time travel storyline featuring the original team and based on story suggestions from editor Tom Brennan.

Parker joked that when he was introduced to the Thunderbolts series, he thought they were a team created by "Thunderbolt" Ross to fight the Hulk that never broke up.

Brennan says that part of the appeal of the series is the camaraderie between the villains; typically when villains team up, you can count down when they're about to fight whereas with these characters, there's a core loyalty to one another.

Parker echoes that sentiment, comparing the Thunderbolts to the mob—it's about having an organization and loyalty.

The contrast between the original team and the new one is that the originals have a loyalty that the government-created one does not and this story may create some union between the latter group.

Artist Declan Shalvey says that some of the original costumes were surprisingly complex and involved a lot of reference to the back issues. He joked that Mark Bagley was changing his mind about the Moonstone design from panel to panel.

Shalvey says he was surprised to find with this arc that it was actually the first time he'd ever drawn the Thunderbolts in New York.

Parker says that during the time travel sequences, while they have to sidestep anything that might date the story, he did ask Shalvey to go a little 90's with the looks of some of the background characters. Shalvey says for one of the women, he went right to Lois and Clark-era Teri Hatcher.

The series actually starts in the aftermath of Onslaught and starts off as though you're reading a 90's Thunderbolts comic.

Brennan says that as a rule, when doing time travel stories it's okay to try to match the art style but referencing anything specific from the period is discouraged.

Without going into specifics, Parker says that the actions in the past will have impact on the Thunderbolts in the present. Brennan says that one of the actions will change the team for the better.

The leadership of both teams is Centurius for the present and Citizen V (Baron Zemo) in the past. Brennan says that in the present, the leadership of the team is kind of diffuse among several members of the team.

Parker says that a major element of the story is the character Fixer trying to find his place on the team and that at some point he "out-leaders" the leadership of the team.

Parker tried to nail down how long in story time has passed between the present team and the original and suggested 10 years. Brennan says it's more like five years.

The biggest surprise for the old team about the new one is for Baron Zemo who notices very clearly that he's not there.

Brennan says that the longevity of Thunderbolts is a credit to the creative talent that has been onboard over the years.